Method of producing adherent metal oxide coatings on metallic surfaces
AssigneeThe United States of America as represented by the Department of Energy
InventorsMichael H. Lane, Robert D. Varrin, Jr.
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Abstract
Provided is a process of producing an adherent synthetic corrosion product (sludge) coating on metallic surfaces. The method involves a chemical reaction between a dry solid powder mixture of at least one reactive metal oxide with orthophosphoric acid to produce a coating in which the particles are bound together and the matrix is adherent to the metallic surface.
Claims25
A process for forming an adherent metal oxide coating, with the ability to withstand severe flow boiling conditions of about 200,000 BTU/hr·ft2 heat flux, on a metallic surface consisting essentially of the steps in this order:
- (a) providing an oxide mixture consisting of at least one reactive metal oxide selected from the group consisting of iron oxides, nickel oxides, zinc oxides and ferrite compounds, having an average particle diameter of from about 1 to about 10 μm and an average surface area of from about 0.5 to about 5 m2/gram;
- (b) ball milling said oxide mixture in a non-aqueous solvent for at least 24 hours and then drying said oxide mixture to form a dry powder mixture;
- (c) combining diluted phosphoric acid with said dry powder mixture to form a coating mixture;
- (d) applying said coating mixture to said metallic surface and,
- (e) heating said metallic surface to form an adherent metal oxide coating on said metallic surface, wherein said phosphoric acid is added in an amount sufficient to produce a porosity of about 20 to about 50% in said adherent metal oxide coating.
A process for forming an adherent metal oxide coating on a metallic surface, with the ability to withstand severe flow boiling conditions of about 200,000 BTU/hr·ft2 heat flux consisting essentially of the steps in this order:
- (a) providing a pre-consolidated oxide mixture comprising at least one of zinc metal powder or iron metal powder, and at least one reactive metal oxide selected from the group consisting of iron oxides, nickel oxides, zinc oxides and ferrite compounds, having an average particle diameter of less than 1 μm to about 10 μm and an average surface area from about 0.5 to greater than 5 m2/gram;
- (b) forming a consolidated oxide mixture combining said pre-consolidated oxide mixture with a concentrated phosphoric acid solution;
- heat treating the resultant mixture to form a solid mass and grinding and sieving said solid mass to a consolidated oxide mixture;
- (c) ball milling said consolidated mixture in a non-aqueous solvent for at least 24 hours and then drying said oxide mixture to form a dry powder mixture;
- (d) combining diluted phosphoric acid with said dry powder mixture to form a coating mixture;
- (e) applying said coating mixture to said metallic surface and,
- (f) heating said metallic surface to form an adherent metal oxide coating on said metallic surface, wherein said diluted phosphoric acid is added in an amount sufficient to produce a porosity of about 50 to about 80% in said adherent metal oxide coating.
Dependencies are inferred from the claim text.